1. Field of the Invention
The present general inventive concept relates to an image forming apparatus and a control method thereof, and more particularly, to an image forming apparatus and a control method thereof to decrease an influence of back surface noise due to an object of a back surface of a document appears on a scan image in scanning a duplex-printed document.
2. Description of the Related Art
Generally, an image forming apparatus having a scan function refers to an apparatus which generates a scan image and prints the image on a printing paper. There is a digital multi-function printer as an example of such an apparatus.
As illustrated in FIG. 1, in an image forming apparatus having a scan function, in order to scan a document and obtain a scan image, a cover 2 is positioned above a document 1, and a fluorescent lamp 3 is operated. Light emitted from the lamp 3 is reflected from the cover 2, permeates a printing paper, and is transferred to an image sensor 4. Accordingly, in a case where the document 1 is a document, in which objects are printed on a front surface and a back surface, i.e., a duplex-printed document, a scan image obtained by the image sensor 4 includes an object 1b on the back surface of the document as well as an object 1a on the front surface of the document.
As such, when a scan image obtained by scanning an object of a desired surface of the document includes an object of an undesired surface, readability with respect to a printing result of printing the scan image is deteriorated.
In order to generate a scan image of good quality, an object of an undesired surface should be removed in a post-processing of scan data obtained by a scan device. Only when a scan image, from which an object of an undesired surface is removed, is printed, a printing result with good readability can be obtained.
When the fluorescent lamp 3 is operated to scan a thin document, light from the fluorescent lamp 3 permeates the document, and is transferred to the image sensor. By this process, an object of an undesired surface appears blurredly on a scan image. Brightness of the object of the undesired surface is between brightness of a text and brightness of a background color. Therefore, if the object of the undesired surface included in the scan image as a normal image is not printed, but the object is treated as the background color, undesired back surface noise can be prevented from being printed.
According to prior art, brightness of a scan image was checked one by one, and then a threshold was set as a reference of treatment of the background color, so as to cope with back surface noise.
However, in the conventional method, in order to check brightness with respect to the entire scan data of one scanned surface and find a superior background color to set a threshold, a memory of a large capacity to store scan data of one surface is needed, and takes a long time to carry out a series of processing operations including setting of a threshold of the background color.
The prior art also discloses checking brightness information of a background color of an upper end portion of a document during an initial scanning process and uniformly treating the background color with respect to the entire region of the document based on the brightness information. In such a case, treatment time may be reduced. However, the treatment of the background color with respect to the entire document may be inaccurately performed, and may cause deterioration of an image quality of a printing result.